Zn含量对Mg-Gd-Zn合金显微组织与力学性能的影响

研究了3种成分的Mg-11Gd-(1,1.5,2)Zn合金的显微组织和力学性能。结果表明,合金的铸态显微组织均由α-Mg基体、(Mg,Zn)3Gd共晶相和14H型LPSO相组成。铸态组织中(Mg,Zn)3Gd相的体积分数随Zn含量的增加而增大,且其热稳定性不断提高。同时,合金中LPSO相的体积分数也随Zn含量的增加而逐渐增大。合金在常温时的抗拉强度随着Zn含量的增加而降低,其中Zn含量较少的Mg-11Gd-1Zn合金在T6处理后呈现最高的强度和良好的塑性。当Zn含量较多时,合金T6处理的效果却远低于T5处理。随Zn含量的增加,合金在200℃高温下的抗蠕变性能也略有下降,但3种合金的抗蠕变性能都优于WE54合金。

Effects of Zn Addition on the Microstructure and Mechanical Properties of Mg-Gd-Zn Alloys

The effect of Zn additions on the microstructure and mechanical properties of Mg-11Gd-(1, 1.5, 2)Zn alloys was investigated by OM, SEM, TEM and electronic universal testing machine. The results show that the microstructure of as-cast Mg-11Gd-(1, 1.5, 2)Zn alloys are composed of a-Mg matrix, (Mg, Zn)3Gd eutectic phase and lamellar 14H-LPSO structure. With the increase of Zn additions, both the volume fractions of (Mg, Zn)3Gd eutectic phase and LPSO phase increase, and the thermal stability of the (Mg, Zn)3Gd phase is improved as well. Tensile tests at room temperature indicate that the strength of as-extruded Mg-11Gd-(1, 1.5, 2)Zn alloys decreases with the increasing Zn content. The Mg-11Gd-1Zn alloy, which contains the lowest Zn among all the alloys studied, exhibits the highest tensile strength with good ductility after T6 treatment. However, the tensile strengths of the Mg-11Gd-1.5Zn and Mg-11Gd-2Zn alloys after T6 treatment are lower than that after T5 treatment. The creep tests at 200 °C/80 MPa reveal that all of the alloys studied have higher creep resistance than the WE54 alloy, and the creep resistance of the alloys decreases gradually with the increase of Zn addition